Equipment such as a mechanical or electrical device may not function properly if it is subjected to moisture or condensation. Enclosures may protect such devices from dripping water on the outside but may not prevent direct condensation from forming inside the enclosure, for example, during extreme temperature cycling. When the environment around an enclosure cools, the inside walls of the enclosure may cool and the air inside may eventually cool. When the inside air cools, the relative pressure inside the enclosure may drop, drawing external air into the enclosure (e.g., through leaks in the enclosure). The external air may be near 100% relative humidity, for example, when the enclosure is rapidly cooled in a rainstorm. The relative humidity of the air inside the enclosure may eventually reach the relative humidity of the air outside the enclosure, and when cooled further, may cause condensation inside of the enclosure.
One type of equipment enclosure is an outdoor video dome for a video camera. A video dome enclosure may be mounted above an area of interest and may have an optically clear or transparent bubble forming the bottom half of the enclosure. An integral pan-tilt-zoom mechanism may be used to observe the area of interest (e.g., parking lots, security gates, building entrances and etc.) usually below and to the sides of the dome. Existing outdoor video dome enclosures may have a condensation problem, especially when located in a coastal humid environment. Condensation on the inside or outside of the bubble may render the dome useless. Condensation on the inside may form a haze on the bubble that obscures the view and may also collect into droplets that run down into the bottom of the bubble to obscure the view. The life of the electronics and mechanical components in the enclosure may also be shortened through corrosion caused by condensation.
Sealed enclosures have been designed to prevent air from entering. Sealed enclosures may leak, however, when subjected to relatively high differential pressures between the inside and outside of the enclosure. Sealed enclosures may be even more difficult to seal when cables need to be run through the walls of the enclosure. A hermetically sealed enclosure solution may work under ideal conditions, but in many cases, is too cost prohibitive and unreliable.